Processes for preparing sulfuric acid are known in various variants from industrial practice. In the melting of the elemental sulfur in the melting stage, emissions occur in the form of offgases which contain, in particular, sulfur dioxide (SO2), elemental sulfur, hydrogen sulfide (H2S) and water. The elemental sulfur present in these offgases can deposit in the form of undesirable solid impurities on cooling in the plant. Furthermore, the sulfur vapors can ignite and therefore represent an explosion risk. In the past, the offgas emissions have frequently been discharged in vapor form via chimneys into the environment. Stricter environmental requirements no longer permit this handling in the case of new plants. Furthermore, subsequently scrubbing the offgases formed in the melting stage is also known. However, a disadvantageously high outlay in terms of apparatus is required for cooling and separating the individual offgas components.
U.S. Pat. No. 2,520,454 A describes a process for preparing sulfuric acid, in which sulfur is vaporized and then burnt in a combustion chamber and oxidized in successive oxidation stages.
Thus a need exists for a process for preparing sulfuric acid by means of which the offgases formed in the melting stage can be treated in a simple and environmentally friendly manner, as well as an apparatus for carrying out this process.